Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 200607
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1007 PM PST Mon Feb 19 2018

.SYNOPSIS...

19/537 PM

Locally gusty winds... light rain... and some mountain snow will
continue into early Tuesday morning. Very cold air will move into
the region tonight and bring freezing conditions to many locations
Tuesday and Wednesday mornings. There is another slight chance of
rain late in the week otherwise conditions will be cool but dry.

&&

.SHORT TERM (MON-THU)...

19/834 PM

A trough of low pressure centered over the Great Basin continues
to slowly exit the region tonight. The trough axis currently over
Los Angeles County currently will move south and east, exiting
the area later tonight. A Winter Weather Advisory remains in
effect as upslope showers could still develop along the northern
slopes of the mountains. A very cold air mass, ushered in with the
trough, will bring cold temperatures to much of the area tonight.
Temperatures in the latest model guidance are trending colder,
which agrees well with the clearing occurring across the coastal
and valley areas this evening. Forecast temperatures will be
trended colder for tonight. A Freeze Warning will likely be
expanded to the Santa Monica Mountains as temperatures will dip
below freezing later tonight and into Tuesday morning along the
interior slopes and mountain valleys. A Frost Advisory is being
considered for the San Fernando and Santa Clarita Valleys. Once
the winds drop late tonight, it will likely trend close to
criteria.

In the San Gabriel Valley, some concern exists for possible
advisory level northerly winds this evening and into late
tonight. High-resolution model solutions hint at the possibility
of wind developing between 9 pm and 3 am. Some of parameters are
consistent with downslope wind research for the San Gabriel
Valley, but the parameters are weaker than the events researched.
Observations are being monitored closely and a Wind Advisory could
be issued later this evening.

*** FROM PREVIOUS DISCUSSION ***

Broad scale cyclonic flow will persist over the area both Tuesday
and Wednesday. Heights will rise but remain below normal.
Afternoon high temperatures across the coast and valleys will be
in the lower to mid 60s each day and will be about 8 to 12 degrees
below normal everywhere in the area.

.LONG TERM (FRI-MON)...

19/210 PM

The GFS and the EC agree that broad scale cold cyclonic flow will
continue over the area through Friday. Both bring an embedded
short wave through the area late on Thursday / early Friday. Much
like today`s system this one will take a dry overland trajectory
and the chance of rain will only be slight. These impulses will
usher in some more cold air along with gusty winds. Max temps
across coasts and valleys will again struggle to reach 60 degrees.

A little pop up ridge will follow on Friday night and Saturday
morning and this should be good for a few degrees of warming but
not as much as possible since hgts will be falling in the
afternoon.

Dry NW flow sets up Sunday. Max temps will be similar to
Saturday`s and there will really not be much in the way of weather
concerns.

A stronger low pressure system is approaching the area by Monday
with the EC bringing some precip into northern SLO county by Tues
00Z, while the GFS is about 18 hours behind it. Not getting
excited by something this far out but it would be much wetter
than what were seeing in the short range...if it happens.

&&

.AVIATION...

20/0605Z

At 0515Z at KLAX, there was no marine layer nor a sfc based
inversion.

High confidence in CAVU conds for the next 24 hours. North winds
at times for most coastal terminals through 12Z. Lgt turbc and or
LLWS possible at all non desert terminals through 12Z.

KLAX...High confidence in CAVU conds for the next 24 hours. There
is a 20 percent chc of a 20 kt x-wnd through 10Z.

KBUR...High confidence in CAVU conds for the next 24 hours.
ocnl lgt turbc and LLWS through 13Z.

&&

.MARINE...

19/823 PM

For the Outer Waters...high confidence in current forecast, with
northwest gales observed at the buoys and models indicating winds
subsiding after 09z. Small Craft Advisory (SCA) level winds
possible on Tuesday and Tuesday night. After a lull on Wednesday,
winds will likely increase to SCA levels again Thursday afternoon
through Friday, possibly continuing into Saturday.

For the Inner Waters...moderate to high confidence in current
forecast, with gales ending by 9 PM, and SCA winds and seas
continuing through late tonight. Large hazardous seas will
gradually subside overnight as the winds diminish. SCA level winds
will be likely again Thursday afternoon and Friday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 2 PM PST Tuesday for zones
      34-35. (See LAXCFWLOX).
     Hard Freeze Warning in effect until 9 AM PST Tuesday for
      zones 34>36-38-44. (See LAXNPWLOX).
     Hard Freeze Warning in effect from 1 AM to 9 AM PST Wednesday
      for zones 34>36-38-44. (See LAXNPWLOX).
     Winter Weather Advisory in effect until 3 AM PST Tuesday for
      zones 38-52>54. (See LAXWSWLOX).
     Freeze Warning in effect until 9 AM PST Tuesday for zones
      39-40-45-46. (See LAXNPWLOX).
     Freeze Warning in effect from 1 AM to 9 AM PST Wednesday for
      zones 39-40-45. (See LAXNPWLOX).
     Frost Advisory in effect until 9 AM PST Tuesday for zones
      88-547. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Tuesday for
      zones 645-650-655. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PST Tuesday for zones
      670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

Rain and snow could return to the area beginning on late Thursday
making travel hazardous in the mountains.

&&

$$

PUBLIC...Hall/jld
AVIATION...Rorke
MARINE...Smith
SYNOPSIS...Kj

weather.gov/losangeles



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